update PyAlias to wrap upstream Alias

src/expr.rs

@@ -122,7 +122,7 @@ impl PyExpr {
     /// Return the specific expression
     fn to_variant(&self, py: Python) -> PyResult<PyObject> {
         Python::with_gil(|_| match &self.expr {
-            Expr::Alias(alias) => Ok(PyAlias::new(&alias.expr, &alias.name).into_py(py)),
+            Expr::Alias(alias) => Ok(PyAlias::from(alias.clone()).into_py(py)),
             Expr::Column(col) => Ok(PyColumn::from(col.clone()).into_py(py)),
             Expr::ScalarVariable(data_type, variables) => {
                 Ok(PyScalarVariable::new(data_type, variables).into_py(py))

src/expr/alias.rs

@@ -19,13 +19,24 @@ use crate::expr::PyExpr;
 use pyo3::prelude::*;
 use std::fmt::{self, Display, Formatter};
 
-use datafusion_expr::Expr;
+use datafusion_expr::expr::Alias;
 
 #[pyclass(name = "Alias", module = "datafusion.expr", subclass)]
 #[derive(Clone)]
 pub struct PyAlias {
-    expr: PyExpr,
-    alias_name: String,
+    alias: Alias,
+}
+
+impl From<Alias> for PyAlias {
+    fn from(alias: Alias) -> Self {
+        Self { alias }
+    }
+}
+
+impl From<PyAlias> for Alias {
+    fn from(py_alias: PyAlias) -> Self {
+        py_alias.alias
+    }
 }
 
 impl Display for PyAlias {
@@ -35,29 +46,20 @@ impl Display for PyAlias {
             "Alias
             \nExpr: `{:?}`
             \nAlias Name: `{}`",
-            &self.expr, &self.alias_name
+            &self.alias.expr, &self.alias.name
         )
     }
 }
 
-impl PyAlias {
-    pub fn new(expr: &Expr, alias_name: &String) -> Self {
-        Self {
-            expr: expr.clone().into(),
-            alias_name: alias_name.to_owned(),
-        }
-    }
-}
-
 #[pymethods]
 impl PyAlias {
     /// Retrieve the "name" of the alias
     fn alias(&self) -> PyResult<String> {
-        Ok(self.alias_name.clone())
+        Ok(self.alias.name.clone())
     }
 
     fn expr(&self) -> PyResult<PyExpr> {
-        Ok(self.expr.clone())
+        Ok((*self.alias.expr.clone()).into())
     }
 
     /// Get a String representation of this column